1. Field of the Invention
The present invention relates to chiral diene ligands, a fabrication method thereof and applications thereof, particularly to a set of bicyclo[2.2.1] chiral diene ligands, a fabrication method thereof, and applications thereof.
2. Description of the Related Art
In the nature, there are many molecules having chiral centers, wherein two molecules having an identical structural formula are mirror-symmetric to each other. A pair of chiral molecules have identical physical properties, such as the melting point, the boiling point and the spectral features, except the light polarization property.
In organisms, many amino acids and enzymes have chiral forms. Normally, a pair of mirror-symmetric isomers (enantiomers) cannot be simultaneously active to a biochemical reaction in an organism. Usually, one of enantiomers is allowed to take part in the reaction inside cells of an organism, but the other enantiomer may be harmful to the organism. For an example, the artificial sweetener D-Aspartame generates sweet taste, but the L-Aspartame generates bitter taste. For another example, the (S)-ethambutol can remedy pulmonary tuberculosis, but the (R)-ethambutol may blind human beings.
Therefore, many scholars are devoted to the development of preparing chiral molecules with high-enantioselectivity to function as intermediates for the syntheses of various biologically active compounds. A common measure thereof is to use a transition metal to catalyze the synthesis of chiral compounds. Normally, ligands with heteroatoms are good chiral modifiers to bind transition metals, forming asymmetric catalysts.
For many organometallic complexes, olefin is often used as the intermediary ligand because olefin has a weaker bonding to the transition metal and is likely to be replaced by heteroatom ligands in fabricating a chiral metal catalyst.
Hayashi, et al. had adopted norbornadiene as the material and used 9 reaction steps to synthesize a bicyclo[2.2.1]heptadiene ligand expressed by Structural Formula (I). The bicyclo[2.2.1]heptadiene ligand is efficacious in catalyzing asymmetric transformations. However, the fabrication thereof is too complicated.
